By “leguminous starch derivative” within the meaning of the invention, is meant any derivative originating from a modification of at least one leguminous starch, chosen from the enzymatic modifications, physical, in particular mechanical, thermal and thermomechanical modifications, and chemical or thermochemical modifications.
By “leguminous starch” within the meaning of the present invention, is meant any starch extracted from legumes, having a high starch content of at least 95% (dry/dry), combined with a low content of colloidal materials and fibrous residues, preferably, less than 1% (dry/dry). The high starch content is preferably greater than 98%.
The protein content is advantageously low, i.e. less than 1%, preferably less than 0.5%, preferably also, comprised between 0.1 and 0.35% (dry/dry).
By “legumes” within the meaning of the invention, is meant the papilionaceae family, the most important representatives of which are firstly the pea, but also the haricot bean, lentil, lupin, broad bean, alfalfa and clover.
By “legumes” within the meaning of the invention, is meant more particularly those for which the amylose content of the starch is less than 60%, in particular comprised between 25 and 55%.
In this group, and according to these considerations, the pea occupies a special position.
Similarly, the invention accords a quite particular place to the dextrins.
By “dextrin” within the meaning of the present invention, is meant a starch modified in dry phase by the action of heat, a combination of heat and a chemical reagent or, optionally, by the action of ionizing radiation.
Numerous methods have been developed, within the context of a rich industrial history, which make use of the action of heat, in a sufficiently dry medium, in the presence or absence of a chemical agent. For the most part, whether they are discontinuous or continuous, they make use of conversion temperatures greater than 100° C. and optionally in the presence of an acid, generally mineral, of an alkaline agent and/or of an oxidizing agent.
The dextrins obtained in the presence of an acid are the most widespread. They are customarily classified in three essential categories containing:                The white dextrins, converted at temperatures often comprised between 120 and 170° C., in the presence of chemical agent(s), in particular of acid, in relatively high quantities,        The yellow dextrins, converted at higher temperatures, often comprised between 170 and 230° C., in the presence of low, or even very low quantities of chemical agent(s), in particular of acid,        The so-called “British GUM” dextrins converted by the action of heat alone, at a high temperature, often greater than 230° C.        
The dextrins obtained by the action of ionizing radiation, which is more recent, are generally not included in this classification.
In most cases, the water content concomitant with the so-called dry phase as understood by a person skilled in the art, is at most equal to a value of approximately 6%.
The methods, considered in a general way, produce different reactions. The importance of each of them varies with essential parameters, such as the level of chemical agent, in particular acid, the initial water content, the temperature profile and the reaction time.
The hydrolysis reaction is significant at the start of the conversion and as from 50° C. Linked to the presence of acid and of a still-sufficient quantity of water, it reduces the molecular mass. It remains important in the conversion of white dextrins.
The condensation or reversion reaction forms an α(1,6) bond from a primary alcohol of one chain and the reducing end of another chain. It is promoted by temperatures less than or close to 150° C.
The “transglucosidation” reaction forming an α(1,6) bond by cutting an α(1,4) bond without releasing water, is predominant at temperatures greater than 150° C. Making it possible to obtain further branched molecules, it is essential to the expression of the properties of the dextrins, in particular, of the yellow dextrins.
Other reactions also take place, such as the internal “anhydration”, between carbons 1 and 6 or the recombination resulting from the reaction between a reducing end and a C2, C3 or C4 hydroxyl group.
The importance, in particular the relative importance, of these phenomena confers specific properties on the dextrins.
Although the dextrin obtained is then, in most cases, subjected to an operation intended to rehydrate it, often to facilitate its dispersion and its dissolution in water, its relation to this solvent contributes to the level of branching achieved, in particular due to the “transglucosidation” reaction.
Although the use of modified starches and dextrins in the paper-making field is described, the literature relating to it is divided. On the one hand, it deals with surface application (Size-Press) operations, most often in the absence of other binding agent and, in particular, of any filler and/or pigment. It also deals with coating, despite the long supremacy of latex and petroleum products.
It is generally considered that a surface application operation designates coating of a paper or folding carton, carried out on a paper machine, starting with a composition the dry matter of which is less than 25%, in particular less than 20%, most commonly less than 15%. Often, the composition is of simple manufacture, comprising only water and soluble polymer.
The pigmented surface application characterizes a surface application composition comprising, in addition, a filler and/or a pigment which occurs only in limited quantities, only slightly modifying the overall dry extract. The latter remains less than 40%, in most cases. It is often less than 30%. The colloidal solutions which constituent the base also have generally less than 25%, often less than 20%, and even 15% dry matter.
By way of reference, there may be mentioned the work “Industrial Uses of Starch and its Derivatives” by J. A. Radley, published by “Applied Science Publishers Ltd.” (1976), page 207 et seq. (chapter V, sub-chapter 5.3) of which are devoted to these aspects.
In the same book, a little further on (sub-chapters 5.6 to 5.9), the coating operations are described, in particular concerned with the modified starches and dextrins. By “coating” is then meant, within the context of the invention, a coating carried out on the basis of a complex composition, most often containing, apart from water, natural and/or synthetic binding agents, fillers, pigments, dispersing agents, rheology- or water resistance-improving agents, optical bleaching agents, and others.
They also relate to compositions the dry extract of which remains modest on certain materials (25 to 45%—page 219). It is higher on most specific machines, greater than 40%, generally greater than 50%, and may reach 65% (same page).
The highest levels of dry extracts of compositions are possible as soon as the concentration of the solutions of modified starches and/or of dextrins is suitable. Within the context of the prior art, the useful concentrations of such sizing agents are, as taught for example by the work of Whistler, Bemiller and Paschall “Starch Chemistry and Technology—Second Edition: Industrial Aspects”, published by Academic Press in 1984, complementary to the previous work, limited to approximately 40%, in particular in the case of conversions carried out at high temperatures (pages 558 to 565), within the context of starch—latex combinations.
These two works provide the essential ideas governing current practices of finishing paper or folding carton by surface application, pigmented surface application or coating produced from modified starches and dextrins. However, the use of such derivatives, originating from leguminous starches is particularly rare.
The use of modified pea starch is recommended in the European patent EP 1 296 790 which in fact only considers pea starches having a high amylose content. In fact it uses the name (“HA pea starch”) without the concept being defined, the description of said patent clearly being insufficient.
In this patent, as in the patent application US 2005/0008801 resulting from it, dry matters of sizing agents appear comprised between 12 and 20%, corresponding to use in surface application at approximately 20%. In any case, these concentrations are highly insufficient for utilization for coating paper.
It appears, on reading the patent EP 0 945 487, previously granted to the same applicants, that by the term “HA” is meant pea starches having an amylose content greater than 60%, the examples stating a higher content, equal to 77.4%.
The contents are crucial for the sought grease-resistance properties, whether in the form of film (EP 0 945 487) or by means of a surface application (EP 1 296 790).
On the other hand, in the U.S. Pat. No. 6,512,108, corresponding to the patent EP 0 945 487, the examples are based, in order to obtain the sought properties, on products having in particular a molecular mass of approximately 2.1.106, deemed too high to achieve the sought optimum viscosity and stability values for both sizing agent and slip.
The European patent application EP 1 281 721 considers dextrins originating from various sources, including the pea, without however assigning it any particular importance, on the contrary. Only the surface application is cited in a context where no technical problem attaches to it.
The applicant has himself described, in the international patent application WO 2005/003456, the use of derivatives of leguminous starches for finishing paper. The description takes into account only limited concentrations of the colloidal solutions and the compositions originating from them, concentrations which correspond to practices of surface application and very little to those of coating.
In fact, the examples are very clear from this point of view, considering only sizing agents prepared with 20% dry matter and coatings by surface application techniques, exclusively, with 15% dry matter.
The solutions proposed in these three documents are manifestly insufficient and do not essentially answer current technical problems. They are limited to grease-resistance and the major context of surface application, in the case of one, and also, essentially, to surface application, in the case of the other two. The extent of the problems encountered is, in fact, much wider and their nature manifestly more acute.
In fact, a real need exists to pay great attention to energy, its availability and its cost. The expense which is connected with this means that amylaceous sizing agents have be prepared with the highest levels of dry matter, such that coating compositions are proposed with the most limited water contents. The increases in dry extract must be compatible with the level of viscosity necessary and useful for the satisfactory operation of the equipment.
It is important to ensure, under these conditions of high dry matter levels, the stability and development of the most limited viscosity, both of the sizing agents and of the coating compositions, in particular faced with the parameters of time and temperature.
Other, environmental aspects lead to the limitation, so far as possible, of the proportion of synthetic materials, in particular latexes, the use of which, as a coating binding agent, is widespread.
Moreover, the difficult supply conditions for potato flour lead to the use of this raw material being avoided.
Taking into account the ideas set forth above must obviously remain compatible with all of the economic and, above all, technical criteria whether these are concerned with preparation, operation of the equipment, specifications relating to the characteristics and properties conferred upon the papers produced.
In any case, a real need exists to reconcile the most acute technical problems encountered by the paper-making industry, in particular within the technical context of coating, as posed in the current demanding environment, and in particular:                to ensure a suitable preparation of the colloidal solution of the amylaceous material with as high a level of dry matter as possible,        to enable, by limited heat inputs to the production of said solution, an initial gain in energy,        to allow, as a result, the production of coating compositions, whatever the objective and in particular, for a finishing of the type of those of the external layer (“top coat”) type, themselves having the highest dry matter levels,        to guarantee, both for the colloidal solution and the composition originating from it, sufficient stability, in particular over time, as desired by a person skilled in the art,        to allow useful energy saving, whether in the making-up of the composition, its deposition on the paper or, above all, its drying, to guarantee, on the other hand, rheological properties suited to the adopted coating technique, such as, in particular, to ensure suitable behaviour of the composition on the machine,        to control the paper's absorption and wettability properties,        to ensure the physical properties required, in particular with respect to roughness, porosity, stiffness, breaking strength,        to supply the optical properties desired for the paper, with regard to its whiteness, its opacity or its gloss,        to guarantee the qualities necessary for correct printing, in particular as regards ink transfer, mottling, soiling or set-off, different faults which may certainly originate in the paper, but also in the roughness and porosity after surface application, in the nature of the binding agents and their possible migration, in the nature of the fillers and pigments which can act and correct the faults described above. In particular, “mottling”, a phenomenon greatly feared by the printer, can be due to factors affecting the paper, whether the support, the composition and its formulation and/or drying, but also parameters relating to the machine, in particular the nature of the ink, the pressure and/or the speed. In these various possible faults, we essentially distinguish between mottling due to ink transfer (“back trap”), mottling due to the superposition of the inks (“trapping”) and wet mottling (action of water).        
All these criteria additionally need to be respected in a satisfactory economic context, both in terms of supply and cost price of the source of starch and the cost of its conversion. These economic data incorporate aspects relating to the other ingredients of the composition, which are necessary because of the performance imperatives.
It is moreover necessary to add to these, the costs connected with the recovery and recycling of the papers.
It is also acceptable to take into account aspects relating to the assumed toxicity and the biodegradability of the materials.
Although documents exist which describe the production of compositions useful to different industries, comprising modified starches and dextrins of various origins, it is noted that, apart from the three documents mentioned above, they consider technical problems unknown to the paper-making fields. Under these conditions, a person skilled in the art of paper-making is not in a position to solve his specific problems.
Nevertheless, established knowledge about the subject-matter has allowed specific approaches such as that described, for example, in the international patent application WO 04/076163, which describes the use of dextrins in sizing agents which can be “activated” with water, in solution or in emulsion. No selection relating to the origin of the starch appears in said document.
The international patent application WO 92/18325 describes biodegradable packaging materials using flours or starches, in particular leguminous. The dextrinization in this case is referred to as partial. It is carried out in an extrusion device, apparently at a low temperature which is not specified. That a plasticizer must be presence constitutes a major parameter leading to the assertion that said operation does not correspond to the concept accepted by a person skilled in the art.
The patent application US 2001/0026827 describes the production of dextrins obtained by thermal conversion of a starch originating from the potato, cassava, haricot bean, cereals such as wheat or corn, including amylose-rich corn starch, excluding green pea starch. They are intended to replace fats or gelatin in manufactured food products.
The international patent application WO 00/41576 describes various starches, in particular modified, including dextrins, which are useful to the food industry as so-called “resistant” starches, but is interested only in the properties specific to the field, without dealing with their production conditions.
Similarly, the U.S. Pat. No. 5,512,311 relates only to the food industries. Although it mentions dextrins, in particular those originating from legumes, it does not define them and moreover prefers certain starch ethers.
The international patent application WO 01/60867 describes a particular heat modification method and only considers a low temperature range comprised between 50 and 120° C., preferably comprised between 65 and 110° C., in particular, comprised between 80 and 100° C. As with the patent application US 2001/0026827, it introduces an unusual raw material amidst the most conventional of starch sources, the haricot bean.
The U.S. Pat. No. 6,423,775, although more specifically interested in the dextrins originating from a leguminous starch, does not define them, the latter constituting only an intermediate product leading to a grafted copolymer originating from said starch.
The French patent application FR 2 309 638 relates to a particular method for the hydrolysis of cereal or leguminous flours, the separation of the proteins being subsequent to the conversion of the starch in an apparently aqueous medium. It is however further linked to the conversion to dextrose and the production of dextrins is not disclosed.
In the article “Indigestible Starch of P. Lunatus by Pyroconversion: Changes in Physicochemical Properties” (Starch/Stärke—June 2004—pages 241 to 247), the authors describe the work carried out exclusively on the Lima bean, under relatively mild dextrinization conditions, in particular in terms of temperatures. The dextrins obtained are assessed with regard to the sole criterion of digestibility, specific to food, compared with that exhibited by other legumes, lentils.
Although the article, taken from Starch/Stärke 49 (1997) “Säureabbau von Stärke unter semi-dry Bedingungen”, considers pea starch, it deals only with an original conversion, in a semi-dry medium, within the context of a very short residence time in a microwave field, making it possible to access modified starches which are useful for replacing fats in the food industry. Such a method, in a semi-dry phase, does not in particular make it possible to reach the desired level of “transglucosidation” of conventional dextrins.
The article “Structural Studies on pea and potato starches using enzymatic methods” (Carbohydrates Europe—March 1999) uses the term “limit-dextrin” for products treated with amylase(s), without specifying their properties and/or intended uses.
In the same way, other articles, such as, for example, “Characterization of Phosphorus in Starch by P-Nuclear Magnetic Resonance Spectroscopy” (Cereal Chemistry 71(5) 488-493, 1994), “Quantitative Measurement of Total Starch in Cereal Flours and Products” (Journal of Cereal Science 20 (1994) 51-58), “Studies on the Structure of Pea Starch”—Parts 1, 2, 3, 4 (Starch/Stärke 45 (1993)) disclose only purely analytical aspects.
On examination of this set of documents, it appears that the modified starches and the dextrins, in particular originating from leguminous starches, which represent, in fact, a very large family, are poorly described, as regards both their nature and their properties. They have above all been studied for the benefit that they bring to the food industry.
As a result, it appears that none of the documents mentioned, or any combination of several of them, makes it possible to solve the technical problems posed by the coating of paper, in particular of the so-called “top coat” type, or to arrive at derivatives having the desired characteristics and properties.